1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device. In particular, the present invention relates to a polishing slurry which can be employed in the formation of a damascene wiring which is made of Cu or W and designed to be employed in a DRAM or a high-speed logic LSI, to the polishing method using the polishing slurry, and to the method of manufacturing a semiconductor device by making use of the polishing slurry.
2. Description of the Related Art
Up to the present, SiO2 and SiN have been employed as an insulating material for LSI. In particular, SiO2 film has been employed as a main insulating film. Whereas, SiN film has been employed as a mask or a stopper on the occasion of removing, for example, SiO2 film by means of RIE (Reactive Ion Etching), or as a barrier film for preventing the diffusion of water and metals.
However, there is a problem that the relative dielectric constant of SiN is as high as 7. In the case of an LSI of the next generation, it is required that, in order to prevent the generation of time lag relative to the operating speed of semiconductor devices, the transmission speed (RC delay) of wirings should be improved. The employment of SiN which has a relatively high dielectric constant is not preferable because of the problem that the capacitance of wirings is caused to increase. Furthermore, there is another problem that the adhesive force of SiN to metals is insufficient.
Under the circumstances, in recent years, the employment of SiC has been studied as a substitute for SiN. The relative dielectric constant of SiC is as low as 5, and the adhesivity thereof to metals is also excellent. Therefore, as far as physical characteristics are concerned, SiC is considered as being an ideal material which is capable of solving the problems that SiN inherently has.
However, even though the relative dielectric constant of SiC is relatively low, it is still higher than that of low dielectric constant insulating materials (porous materials) whose relative dielectric constant is within the range of 2.2 to 2.8. Therefore, it is required, when a multi-layer wiring is to be actually formed, to eliminate as much as possible any superfluous portion of SiC which is no longer required to be left as an adhesion layer or as a barrier layer.
However, no one has yet succeeded to find a suitable polishing method which makes it possible to easily remove SiC. Therefore, it is strongly desired, particularly in the formation of a multi-layer wiring, to find a method which makes it possible to easily remove a superfluous portion of SiC.